Field of the Invention
The present invention relates to the field of turbojet engines.
Description of the Related Art
A multi-flow (for example, dual flow) turbojet engine, for propelling transport aeroplanes, generally comprises an upstream fan delivering an annular air flow, this flow comprising a primary, central, annular portion that supplies the engine driving the fan, together with a secondary, outer, annular portion, intended to be exhausted into the atmosphere while providing a considerable fraction of the thrust.
In order to compress this annular air flow, the turbojet engine is fitted with a set of wheels provided with blades of large dimensions, which are fixed to discs by means of bulbs and recesses with which each of the discs and blades is provided, the bulbs of the disc having a complementary shape to that of the recesses of the blade and being capable of cooperating therewith, the recesses of the disc having a complementary shape to that of the bulbs of the blade capable of cooperating therewith.
Because the use of the turbojet engine is limited by temperature, the end of the disc, which constitutes the part of the disc nearest to the flow path, must be cooled.
Currently, this cooling is produced by a cooling air flow passing into the bottom of the recesses of the disc. To this end, each bulb of the blade is arranged relative to one of the recesses of the disc so as to contrive between them, when said bulb cooperates with said recess, a main channel through which the cooling air flow can pass, a foil also being positioned between said disc and said blade. This air flow, having crossed the main channel, and thus having cooled its boundary area, can then be exhausted into the annular air flow.
In this configuration, the cooling air flow mainly allows the recess and the bottom of the bulb of the disc to be cooled, to the detriment of the apex of the bulb. However, the apex of the bulb constitutes the most thermally stressed zone of the disc and therefore requires the most cooling. Consequently, cooling of the disc is not currently effective.